There is interest in methods for the synthesis of large numbers of diverse compounds which can be screened for various possible physiological or other activities. Techniques have been developed in which one adds individual units sequentially as part of the chemical synthesis to produce all or a substantial number of the possible compounds which can result from all the different choices possible at each sequential stage of the synthesis. Numerous strategies have been devised for producing such combinatorial libraries (R. M. Baum, Combinatorial Approaches Provide Fresh Leads for Medicinal Chemistry, C&EN, 20-25, Feb. 7, 1994). Common to many of these strategies is a technique known as split synthesis (Furka et al., "Cornucopia of Peptides by Synthesis", Abstr. 14th Int. Cong. of Biochem., Prague Czechoslovakia, Vol. 5, p 47 (1988) and "More Peptides by Less Labour", Abstr. 10th Int. Sym. on Med. Chem., Budapest, Hungary p 288 (1988)), which essentially comprises dividing a first pool of material into sub-pools, treating these sub-pools so as to effect a change in the material, mixing the sub-pools into a second pool, and then again dividing the changed material into a new set of sub-pools for further treatment. This process is iterated until the desired end products are produced. Ideally, every theoretical member of the library is produced by this synthesis on solid supports, where each solid support holds an individual member, and these members are present in equal number, i.e., in the final pool there is an equal number of members for every possible combination of reactions. However, a perfectly even splitting is not achieved and this can lead to the non-production of some members and an over or under production of others. Over or under production of members can lead to other errors. For example, in deconvolution analysis of combinatorial libraries over or under representation of library members can be misinterpreted as indicating strong or weak compounds, e.g., in a binding assay, and result in the further elaboration of uninteresting compounds. One way to reduce the first of these possibilities (non-production) is to design for an excess amount of each member in these syntheses, typically 10-1000 fold redundancy. However, this approach does not affect the over or under production of certain members. Even with redundancy there is a calculable error (.sigma.) from the ideal. Reduction of this error is desirable.